CCNP / BSCI Examination Tutorial: Route Summarization As well as the OSPF Null Interface
CCNP exam results, specially within the BSCI exam, demands you realize the main points of route summarization. This skill not just requires you have a convenience degree with binary conversions, but You will need to know how and where to apply route summarization with Every specific protocol.
You even have to understand the “Unwanted side effects” of route summarization. With OSPF, there will actually be an extra interface made at The purpose of summarization, and this catches lots of CCNP candidates by surprise. Allow’s Examine the null0 interface And exactly how it relates to OSPF summarization.
On R1, the next networks are redistributed into OSPF, and afterwards summarized.
interface Loopback16
ip handle sixteen.16.16.sixteen 255.0.0.0
interface Loopback17
ip deal with seventeen.seventeen.seventeen.17 255.0.0.0
interface Loopback18
ip address eighteen.eighteen.eighteen.eighteen 255.0.0.0
interface Loopback19
ip handle 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute linked subnets
R1(config-router)#summary-handle sixteen.0.0.0 252.0.0.0
The summary deal with appears on R2, a downstream router.
R2#exhibit ip route ospf
O E2 16.0.0.0/six [one hundred ten/20] via 172.twelve.123.one, 00:00:05, Serial0
Permit’s go back to R1 and look at its OSPF table.
R1#display ip route ospf
O sixteen.0.0.0/six 토토사이트 is actually a summary, 00:01:fifty one, Null0
Where by did the null0 interface come from, and why could it be there? Packets sent towards the null interface are dropped, and In such cases, that’s a great matter.
Once you configure summary routes in OSPF, a route to null0 will likely be mounted in to the OSPF routing table. This allows to stop routing loops. Any packets destined to the routes that were summarized will have an extended match while in the routing table, as demonstrated below…
C seventeen.0.0.0/8 is specifically linked, Loopback17
C 16.0.0.0/8 is straight connected, Loopback16
C 19.0.0.0/8 is specifically related, Loopback19
C 18.0.0.0/eight is instantly linked, Loopback18
O sixteen.0.0.0/6 is often a summary, 00:01:fifty one, Null0
.. and packets that don't match among the summarized routes but do match the summary route will be dropped.
Avoiding routing loops when performing route redistribution and summarization is vital. OSPF gives us slightly assist in that regard in this example, and when you research additional advanced redistribution situations with your solution to the CCNP and CCIE, you’ll know that we’ll acquire all the assistance we can get!